Question

find the sum of the arithmetic sequence having the data given.

a1 = 5, an = 3, n = 20

Answer 1

Do you know which formula to apply?

Answer 2

I have no idea, I missed a few days of class and I came back to a whole new lesson. Kinda just tryin to get caught up right now

Answer 3

S_n = n ( a_1 + a_n ) / 2

Answer 4

chloro right

Answer 5

Do you know how to plug in?

Answer 6

nuh uh :/

Answer 7

Try a1 = ?

Answer 8

that easy

Answer 9

i can prove formula

Answer 10

Just go step by step!

Answer 11

no, sum sequense have formula, not step by step

Answer 12

@Adam1994 pls let me know a1?

Answer 13

a1=5

Answer 14

a_n?

Answer 15

ok, i know a litle english

Answer 16

a_n = 3

Answer 17

Would you double check this problem, I believe it's wrong!

Answer 18

Since n = 20 => we're looking for S_20

Answer 19

S_20 = 20 ( a_1 + a_20 ) / 2

Answer 20

Anyway, this is the formula for arithmetic Sum, just memorize it for your own benefit!